30.06.2013 Views

multiple time scale dynamics with two fast variables and one slow ...

multiple time scale dynamics with two fast variables and one slow ...

multiple time scale dynamics with two fast variables and one slow ...

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

whereα,β1 <strong>and</strong>β2 are:<br />

α(t) = C|a|( ˆX+ǫ(1+ ˆZ))<br />

β1(t) = −µ+ C(δ+|a| ˆX)<br />

β2(t) = K[(ǫ+|b|+ǫ|a| ˆX) ˆZ+ǫ+|b|]<br />

The constantµ>0 carries over from Lemma 2.5.1 <strong>and</strong>δ>0 defines the neighbourhood<br />

size of B as given in (2.22).<br />

Proof. We start by proving (2.31). A direct calculation as in the previous lemma<br />

gives<br />

| ˆZi| ′ =− η11 ˆZ 2 ˆZi<br />

i<br />

+η1i<br />

Z1| ˆZi| Z1| ˆZi|<br />

(2.33)<br />

The chain <strong>and</strong> quotient rules used for calculating (2.33) are only valid for|Zi|0,<br />

when Zi=0 we only obtain left <strong>and</strong> right limits for the derivative of opposite<br />

sign. If we estimate the right-h<strong>and</strong> side of (2.33) then<br />

| ˆZi| ′ <br />

<br />

<br />

≤<br />

η11<br />

<br />

<br />

<br />

<br />

| <br />

<br />

<br />

ˆZi|+<br />

η1i<br />

<br />

<br />

<br />

<br />

<br />

Z1<br />

which is independent of such left <strong>and</strong> right limits. Using Lemma 2.5.1 again we<br />

find<br />

<br />

<br />

<br />

<br />

<br />

<br />

<br />

<br />

<br />

<br />

η11<br />

Z1<br />

η1i<br />

Z1<br />

<br />

<br />

<br />

<br />

≤ ˜C|a|(1+ˆX)+ǫ ˜K|a|(1+ ˆZ+ˆX)<br />

<br />

<br />

<br />

<br />

≤ ˜C|a|(| ˆZi|+ˆX)+ǫ ˜K|a|(1+ ˆZ+ˆX)<br />

The desired estimate (2.31) now follows if we choose C again such that C ><br />

˜C+ǫ ˜K <strong>and</strong> C> ˜K. This completes the first part of the proof. For the second part<br />

we again use calculus first:<br />

ˆX ′ i = d<br />

dt<br />

Xi<br />

Z1<br />

<br />

= Z1X ′ i<br />

Z1<br />

′ − XiZ 1<br />

Z2 1<br />

= Z1(BiiXi+η2i)− Xi(ΛZ1+η11)<br />

= (Bii−Λ) ˆXi+<br />

47<br />

Z2 1 <br />

η2i<br />

Z1<br />

− η11<br />

Z1<br />

ˆXi

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!